1. Field of the Invention
The present invention relates generally to an electrostatic filter for non-conductive liquids; and more particularly to an electrostatic filter for removing particulate contaminants from turbine and hydraulic oils, synthetic fluids such as silicon oil, phosphate and silicate ester based oils, brake fluid, heat transfer fluids, transmission fluids and other natural and synthetic based fluids.
2. Description of the Prior Art
Conventional filter technology is based on the mechanical ability of a strainer or composition filtering material to remove contaminants that may vary in size from 1 micron to 100 micron and larger. While these filters can remove most of the particulate above 10 micron, their effectiveness on removing particulate of 10 micron size and below is hindered either by the filters design or the high pressure differential due to the accumulation of particulate in the filtering media. The filtration performance of this technology is limited by the pore size of the media. Only particles larger than the filter pore size will be removed, smaller than the pore size particulate collide with each other thus forming larger particulate and hence exasperating the pressure differential problem in the mechanical filter. In contrast, passing fluid through the electric charged field of the subject filter, where positive charged particulate migrate to the negative plate and negative charged particulate travel to the positive plate, there is no discrimination as to the type or size of particulate that can be removed. The prior art includes various designs of electrostatic filters that have evolved over the years. These filters still present a number of problems in terms of fabrication, testing, ease of replacement and safety of replacement. Additionally, some designs make no provision to remove colloidal contaminants chains, attendant arcing and subsequent unloading of the contaminant accumulation from the electrodes.
It has previously been proposed in the patent of Thompson U.S. Pat. No. 4,594,138 to provide a complex fabrication with nails placed through a plastic disposable cylinder housing to properly position electrodes at a respective distance to establish an inter-electrode space. Reproducing this design presents several readily apparent obstacles. U.S. Pat. No. 4,800,011 to Abbott-Durossette presents a complex, costly, disposable filter requiring blind insertion of plastic spacers of insufficient diameter to prevent distortion of the electrode during fabrication. Both of these designs flow fluid parallel to the line of force and transverse through the electrodes without sealing between the outside diameter of the electrode and the inside diameter of the plastic, disposable housing. This permits contaminated fluid to migrate through this open space, bypassing the route through the small holes provided in the electrode and hence diluting the performance of this design filter. Colloidal suspensions of particulate through these designs travel as a chain thus bridging the space between the electrodes and electrically grounding the system.